Cyclic trellis coded modulation

Abstract

A universal method of trellis encoding signals mapped according to any signal constellation format involves constructing an encoder output table and a state transition table. The encoder output table defines the output symbol of an encoder given the input symbol and the present state of the encoder, while the state transition table defines the next state of the encoder given the present state of the encoder and the input applied to the encoder. The output table and the next state table are constructed with the objective of providing maximal distances between the branches of the trellis diagram without any regards for the shift register implementation of the code. Cyclic trellis-coded modulation is an example of such codes without feed-forward or feed-back shift register implementations, and with equal or better performance than “optimal” shift register trellis codes with 16 states or less. The cyclic trellis codes for both AWGN and Rayleigh fading applications can be constructed for any signal constellation without resorting to exhaustive searches.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This is a continuation of prior application serial number 10 / 039,038 filed Jan. 4, 2002 U.S. Pat. No. 6,578,173, which is a continuation of application 09 / 146,982 filed Sep. 3, 1998 now abandoned, which is a continuation of Ser. No. 08 / 581,477 filed Nov. 17, 1995 now U.S. Pat. No. 5,907,565 issued May 25, 1999, which is a divisional of 08 / 344,111 filed Nov. 23, 1994 now U.S. Pat. No. 5,675,590 issued Oct. 7, 1997 to which a claim for priority is made and which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to digital communication systems, and, in particular, to forward error correction through trellis coded modulation.BRIEF DESCRIPTION OF THE RELATED ART[0003]In recent years, much of the research and development in the communications industry has been concentrated in the area of digital signal transmissions. As is well known in the art, digital signal transmission typically involves transmi...

AI Technical Summary

Benefits of technology

[0023]A trellis encoder constructed in accordance with the teachings of the present invention can be adapted to trellis encode data to be mapped for signal constellations. The signal constellations can be set partitioned such that each level of set partitioning results in substantially increased minimum Euclidean distance between points of the signal constellation. The trellis encoder can also be adapted to trellis encode data to be mapped for signal constellations which cannot be set partitioned such that each level of set partitioning results in substantially increased minimum Euclidean distance between points of the signal constellation.

Problems solved by technology

The growing demand for access to data and communication services has placed a significant strain on the available bandwidth.

An increase of the rate of the data typically results in an increased bandwidth requirement, placing a further strain upon the available bandwidth for transmission of signals.

These high level modulation schemes are very sensitive to channel impairments.

That is, the information encoded by means of such techniques is often lost during transmission due to noise, Rayleigh fading and other factors which are introduced over the communication medium.

However, designers of past systems have not considered providing a technique of trellis coding which applies to any phase and / or amplitude modulation scheme, as well as codes having various constraint lengths, while providing optimal or near optimal error performance.

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